Wash, stalk and stone the cherries. Rinse blackberries, sort and dab dry. Weigh a total of 1 kg fruit.
Bring the fruit and jam sugar to the boil in a large pot over high heat while stirring. Then boil for about 3 minutes while stirring constantly. Stir in the genever.
Pour hot jam into prepared twist-off jars. Seal immediately and let cool upside down.